Production of high octane gasoline from coal liquids

ABSTRACT

A HIGH OCTANE GASOLINE IS OBTAINED, WITHOUT ADDITION OF LEAD-CONTAINING COMPOUNDS, BY THE HYDRO-TREATING AND CATALYTIC CRACKING OF COAL-DERIVED LIQUIDS. A HEATING OIL STREAM OBTAINED FROM THE CATALYTIC CRACKING STEP IS RECYCLED TO THE HYDROTREATER, RUSULTING IN AN IMPROVEMENT IN THE RESEARCH OCTANE NUMBER (CLEAR; I.E., MEASURED WITHOUT ADDITION TO TETRAETHYL LEAD) OF THE NAPHTHA OBTAINED FROM THE COAL-DERIVED LIQUID. HYDROCRACKING OF THE HEATING OIL, WITH THE RESULTANT REDUCTION IN OCTANE NUMBER, IS AVOIDED. CATALYTIC CRACKING WITH A MOLECULAR SIEVE CONTAINING CATALYST IS PREFERRED, BECAUSE OF ITS HIGHLY SELECTIVE ACTION IN DENITROGENATING THE HEATING OIL STREAM.

Oct. 24, 1972 y B. l.. scHuLMAN 3,700,586

PRODUCTION OF HIGH OCTANE GSOLINEv FROM COAL LIQUIDS Filed Aug. 1o, 1970 Nz mm.. @Nn

INVENTOR, BERNARD L. SCHULMAN,

ATTORNEY United States Patent Oftice Patented Oct. 24, 1972 3 700 586 PRODUCTION F nuGii ocTANE GAsoLiNE FROM COAL LIQUIDS Bernard L. Schulman, Livingston, NJ., assignor to Esso Research and Engineering Company Filed Aug. 10, 1970, Ser. No. 62,301

Int. Cl. Cg 23/00 U.S. ICI. 208-89 10 Claims ABSTRACT 0F THE DISCLOSURE A high octane gasoline is obtained, without addition of lead-containing compounds, by the hydro-treating and catalytic cracking of coal-derived liquids. A heating oil stream obtained from the catalytic cracking step is recycled to the hydrotreater, resulting in an improvement iii the Research Octane Number (clear; i.e., measured without addition to tetraethyl lead) of the naphtha obtained from the coal-derived liquid. Hydrocracking of the heating oil, with the resultant reduction in octane number, is avoided. Catalytic cracking with a molecular sieve containing catalyst is preferred, because of its highly selective action in denitrogenating the heating oil stream.

BACKGROUND OF THE INVENTION (l) Field of the invention The present invention is directed to a process for obtaining a high octane gasoline from a coal-derived liquid, avoiding the need for addition of lead-containing compounds. By the present invention, the use of hydrocracking and subsequent reforming of the coal-derived liquid is avoided, making the process more economically attractive.

(2) Description of the prior art The production of gasoline from coal-derived liquids is well known in the art. The liquid oil stream which is obtained from coal liquefaction is obtained either by hydrogen-donor solvent liquefaction as shown in the Gorin patents 3,018,241, 3,018,242, and 3,117,921, or as obtained by the catalytic liquefaction scheme shown in Johanson Re. 25,770. The prior art, as exemplied in the Gorin Pat. 3,143,489 produces a gasoline fraction by hydrocracking the coal liquid in one or more zones. In the 489 patent, the coal-derived liquid is hydrocracked in a primary hydrocracking zone, passed through a hydrogen refining zone, and is ultimately hydrocracked again in a secondary hydrocracking zone. In spite of the highly aromatic nature of coal liquids, the gasoline obtained by hydrocrackin-g is low in aromatics (the hydrocrackate is essentially completely hydrogen-saturated) and requires a subsequent catalytic reforming step or the addition of a lead-containing compound (or both) in order to make it commercially usable. The present process produces a high octane naphtha without resort to either of these expedients.

SUMMARY OF THE INVENTION The present invention is directed to a process for producing a high octane gasoline from a coal-derived liquid, avoiding the addition of lead-containing compounds or the use of an expensive reforming operation.

The supply of domestic petroleum stocks as compared to demand has been declining over the years. The need for a supplemental source of liquid hydrocarbon fuels is becoming clear, and the domestic deposits of coal appear to provide the most attractive source for such hydrocarbon fuels. At the same time, the need for avoiding the atmospheric pollution is receiving wide attention, and suggestions have been made by some that the use of lead-containing gasoline additives should be avoided or reduced.

The present invention is directed to a solution of both problems, providing an economically attractive process fOr producing high octane gasolines from coal-derived liquids, while at the same time avoiding or minimizing the need for lead-containing additives. The present invention involves the hydrotreating and catalytic cracking of a coal-derived liquid, recycling to the hydrotreater the heating oil fraction and, preferably, the bottoms obtained as a result of the catalytic cracking. By the present invention a catalytic naphtha having a Research Octane Number in the area of 99 (clear) can be obtained, without the use of expensive catalytic reforming operations as heretofore thought to be necessary.

A coal-derived liquid stream is hydrotreated to increase the hydrogen content to about 9 to 10 weight percent, to remove from to 90 weight percent of the sulfur compounds present in the feedstock, and to remove from 30 to 60 weight percent of the nitrogen present in the feedstock. The hydrotreated product is catalytically cracked under mild conditions to obtain a naphtha product, a heating oil product, and a bottoms product. The heating oil product and the bottoms product can be recycled virtually to extinction, while the naphtha product, high in aromatic content, is a 99 RON (clear) gasoline blend stork containing about 10.5 weight percent combined hydrogen. It has been found that the catalytic cracking step preferentially reduces the nitrogen content of the heating oil fraction, making it possible to recycle all of the heating oil into the hydrogenating zone, thereby diluting the inhibiting eiect of ammonia formation which is concomitant with the denitrogenation of the fresh feed. As a consequence, the hydrogen content of the total hydrotreating product can economically be increased to that level at which coke laydown in the catalytic cracking zone is acceptable but without reducing aromaticity of the product to any substantial degree.

It has been found that the hydrogen content of a coalderived liquid is directly related to the amount of coke which will be for-med therefrom in a catalytic cracking reactor. As shown below, in Table I, the carbon yield in low severity catalytic cracking is dependent upon the amount of hydrogen in the liquid feed to the catalytic cracking unit. The table indicates that at about 9 to 10 Weight percent hydrogen in the liquid feedstock, the carbon yield 1 At 40% conversion.

The coal-derived liquid normally contains from about 6.5 to about 7.5 weight percent hydrogen. Thus, it is necessary to add hydrogen by way of hydrotreating if the amount of carbon laydown in the catalytic cracking unit is to fall within acceptable limits. The amount of hydrov gen added should not, however, be so great as to destroy the essentially aromatic character of the coal-derived liquid, since it is in this aromatic character which makes it possible to obtain the high octane naphtha from the catalytic cracking step. The coal-derived liquid contains about 90 weight percent aromatic compounds. After hydrotreating, it contains about weight percent of aromatics. For e'cient hydrogenation to the desired levels, a hydrotreating zone should be operated under conditions allowing the hydrogenation activity of the catalyst to be ecieritly employed. However, as is well known in the art, hydrotreating also acts to remove sulfur and nitrogen. The nitrogen is removed in the form of ammonia, and this ammonia acts as an inhibitor for the hydrogenation activity of the catalysts which are employed. Therefore, the amount of nitrogen in the net feedstock to the hydrotreater should be kept as low as possible.

By the present invention, it has been found that the nitrogen content in the heating oil fraction is reduced not only by the hydrotreater but also during catalytic cracking so that a heating oil recycle stream will contain only about 0.02 weight percent nitrogen, as compared to about 0.35 weight percent in that fraction of the original fresh feed. Thus, recycle of the heating oil will dilute the total nitrogen content of the feed into the hydrotreating zone, thereby minimizing the effects of ammonia formation and allowing the hydrogenation activity of the catalyst to be maximized. Further, the recycle of the heating oil allows the hydrogen content thereof to be increased, facilitating the catalytic cracking of that heating oil.

By contrast to the present invention wherein the hydrogen content in the naphtha fraction is increased to about 10.5 percent, the naphtha from a hydrocracking zone is about 14 percent hydrogen. This indicates an aromatics content in the naphtha of the present invention of about 60-80 weight percent as compared to about 10-30 weight percent aromatics in the naphtha obtained from a hydrocracking zone. The Research Octane Number of the naphtha obtained from a hydrocracking zone is about 65 to 70 (clear) as compared to the 99 (clear) R.O.N. of naphtha obtained by the present invention.

The present invention will be better understood by the following discussion.

Feedstock.-The present invention is directed to the treatment of a fresh feedstock which is a liquid oil stream from the liquefaction of coal. Preferably, the coal will be liquefied by contact with a hydrogen-donor solvent generally as described in U.S. Pats. 2,018,241 and 2,018,242, although the catalytic liquefaction disclosed in Re. 25,770 can instead be employed. The liquid oil feedstock to the process of the present invention will have a boiling range within the limits from about 400 to about 1000 F., with a 50 percent point of at least about 600 F. The hydrogen content of the fresh feed may vary from about 6.5 to about 8.0 weight percent; however, typically it will be about 7.2 weight percent. The sulfur content of the fresh feed may range from 0.2 to 2.0 weight percent; nitrogen content, from 0.3 to 1.5 weight percent; and aromatics content, from 50 to 90 weight percent. A typical feed stock, obtained from the hydrogen-donor solvent liquefaction of an Illinois No. 6 coal is shown below in Table Il TABLE II Boiling range: 500/ 1,000 F.

In the present process, fresh feed is admixed with a recycle stream before introduction into the hydrotreating zone. The recycle stream may contain heating oil (430/650" F.) and the bottoms stream (650 F.+) obtained by fractionation of the products of the subsequent catalytic cracking zone. The recycle heating oil may comprise from 25 to 45 volume percent of the total liquid feedstock into the hydrotreating zone, preferably 35 percent. The bottoms typically will constitute from 10 to 25 weight percent of the total feedstock into the hydrotreating zone, preferably about volume percent. When the preferred total recycle of both streams is employed, the

21 nitrogen content of the net hydrotreater feedstock is about 0.37 weight percent, if a fresh feed having a nitrogen content of 0.7 weight percent is employed. Thus, the effective rate of ammonia formation will be reduced by onehalf and the hydrogen content of the recycle streams increased, leading to benefits in both the hydrotreating and the cracking steps.

Hydrotreating.-A mixed feedstock is subjected to mild hydrotreating in a hydrotreating zone wherein there is only a slight lowering of the boiling range as the hydrogen content is increased, and the sulfur and nitrogen contents are decreased. The aromatics content of the feedstock is only slightly reduced, due to the mild hydrotreating conditions.

The hydrotreating catalysts employed herein are of the conventional variety. Without being limited to any particular catalyst, these catalysts will typically comprise an alumina or silica-alumina support carrying one or more iron group metals and one or more metals of Group VI-B of the Periodic Table inthe form of the oxides or sulfdes. In particular, combination of one or more Group VI-B metal oxides or sullides with one or more Group VIII metal oxides or suliides are preferred. For example, typical catalyst metal combinations contemplated are oxides and/or sullides of cobalt-molybdenum, nickeltungsten, nickel-molybdenum-tungsten, cobalt-nickelmolybdenum, nickel-molybdenum, etc. As a typical example, one catalyst will comprise a high metalcontent sulfded cobalt-molybdenum-alumina catalyst containing -about 1 to l0 weight percent cobalt oxide .and about 5 to 40 .weight percent molybdenum oxide, especially about 2 to 5 weight percent cobalt and about 10 to 30 weight percent molybdenum. It will be understood that other oxides and suldes Will be useful, such as those of iron, nickel, chromium, tungsten, etc. The preparation of these catalysts is now well known in the art. The active metals can be added to the relatively inert carrier by impregnation from aqueous solutions followed by drying and calcining to activate the composition. Suitable carriers include, for example, activated alumina, activated alumina-silica, zirconia, titania, etc., and mixtures thereof. Activated clays, such as bauxite, 4bentonite and montmorillonite, may also be employed.

The operating conditions in the hydrotreating zone are such that a mild hydrotreat is obtained. These conditions include a temperature from about 675 to about 775F. (preferably about 720 F.), a pressure from about 1,500 to about 3,500 p.s.i.g. (preferably about 2,000 p.s.i.g.), a liquid hourly space velocity (LHSV) from about 0.2 to about 1.0 (preferably about 0.4) v./v./hr., a hydrogen treat rate from about 5,000 to about 15,000 s.c.f./b. (preferably about 10,000 s.c.f./b.), and a hydrogen uptake from about 1,000 to about 3,000 s.c.f./b. (preferably about 2,000 s.c.f./b.). Hydrogen purity in the treat gas may range from 60 to 95 mol percent, preferably about mol percent. The hydrotreating reaction is enhanced by the dilution elfect of the recycle gas oil stream as above discussed. Typical hydrotreater feed and product inspections are shown below in Table III. The feed is a combined stream consisting of the coal liquid shown in Table II in admixture with recycled heating oil and bottoms.

From the above table, as compared to Table II, it can be seen that the introgen content and sulfur content of the feed are decreased substantially, while the aromatics content is only slightly reduced. The hydrogen content has, however, been increased from 7.5 weight percent to about 9.7 weight percent, making the total hydrotreated product suitable as a feedstock into a catalytic cracking zone.

Catalytic cracking-The catalytic cracking reaction is carried out at low severity, so as to obtain a good yield of the high octane naphtha product with a minimum of coke and gas. The catalytic cracking can be carried out as is well known in the art in a uidized bed or in a transfer line, with the oil feedstock in the vapor phase. The low severity operations are carried out at a once-through conversion from about 25 to about 50 percent. The conversion is expressed as the percent of 430 F.+ components in the feedstock which are converted in a single pass through the reactor into materials boiling lower than 430 F. and is referred to hereinafter as once through 430 F.+ conversion. Any suitable catalyst such as silica alumina, silica magnesia, and cracking clay can be used. However, the preferred catalysts for the 'present process are the crystalline alumino-silicate zeolite types. In general, the -chemical formula of the @anhydrous crystalline zeolites employed in the present invention expressed in terms of moles may be represented as:

wherein Me is selected from the group consisting of metal cations, hydrogen and ammonia, n is its valence and X is a number above 3, e.g. 4 to 14, preferably 4.5 to 6.5. The zeolites include synthetic crystalline aluminosilicates, naturally occurring crystalline aluminosilicates and treated clays in which a substantial portion of the clay has been converted to crystalline zeolite. Synthetic materials include faujasites and mordenites. Natural materials are erionite, analcite, faujasite, phillipsite, chinoptilolite, chabazte, gmelinite, mordenite and mixtures thereof containing or treated to contain S to 95 percent crystalline aluminosilicate having an ordered structure. All or a portion of the cations of the zeolites such as sodium cations can be replaced with hydrogen ions, ammonium ions or metal cations such as rare earths, manganese, cobalt, zinc and other metals of Groups I to VIII of the Periodic Table. The catalyst can be one of the matrix types, i.e., one in which the zeolite crystals are coated with or encapsulated in a silecous or silica-alumina gel. Matrix catalyst contain 5 to 60 percent, preferably 5 to 20 percent, crystalline zeolite.

Operations of the catalytic cracking zone will be generally the same as those known to those skilled in the art, carried out under low severity (that is, low conversion) conditions. The conditions employed may include a temperature from about 875 to about 1050 F. (preferably about 950 F.), a pressure from about 5 to 60 ratio from about 5 to about 25 pounds per pound (preferably about 15 pounds per pound), and oil residence time from about 1S to about 60 minutes (preferably about 30 minutes), and a once-through 430 F.+ conversion from about 25 to about 50%, preferably about 40%.

From the catalytic cracking reactor, the oil product is separated from the catalyst and conducted into a fractionator wherein it is separated into at least three streams: a naphtha stream, a heating oil stream, and a bottoms stream. The naphtha stream will boil within the range from C5 to about 430 F., and will constitute about 35 to 55 volume percent (e.g., about 45 volume percent) of the total fractionator C5+ feed. The heating oil will boil from about 430 to about 650 F., and will constitute from about 3() to about 50 volume percent (e.g., about 40 volume percent) of the total fractionator feed. The bottoms will contain those compounds boiling higher than about 650 F., and will constitute from about 10 to about 30 volume percent (e.g., about l5 volume percent) of the total fractionator feed. The inspection data of typical fractionator product streams are shown below in Table IV.

The heating oil stream is suitable for sale, or for further conversion to high octane naphtha by other methods, such as by hydrocracking and catalytic reforming, if desired. However, as previously stated, it is much preferred for the low nitrogen content heating oil to be recycled in the present invention, so as to contribute to the production of high octane naphtha product. From about 0 to 100% of the heating oil stream from the fractionator will be recycled to the hydrotreating zone, preferably all of such gas oil being so recycled. The bottoms stream is also preferably completely recycled to the hydrotreating zone, although from 0 to 100% thereof may be withdrawn for use or sale.

DISCUSSION OF PREFERRED MODE Referring to FIG. l, the process of the present invention is schematically shown. The fresh feed is introduced into the system by way of lines and 102. Through line 100 is introduced a S50-700 F. cutl from a coal liquid. In the exemplary embodiment, 133,000 lbs./hr. of this stream are charged. This fraction will contain 0.35 weight percent nitrogen and 7.8 weight percent hydrogen. Through line 102 are introduced 328,000 lbsl/hr. of the 700 F.+ material from the liquefaction of coal. This stream contains 0.85 weight percent nitrogen and 6.7 weight percent hydrogen. When operating in the preferred mode, all of the gas oil and bottoms from the catalytic cracking fractionator will be recycled so that the feed stream to the hydrotreater will also include 245,000 1bs./ hr. of the 430-650 F. stream as indicated by line 104. This stream contains 0.02 weight percent nitrogen and 8.6 weight percent hydrogen. Through line 106, 116,000 lbs./ hr. of the bottoms stream will be recycled. This stream contains the 650 F.+ material from the fractionator and contains 0.26 weight percent nitrogen and 6.4 weight percent hydrogen. The hydrotreater also receives 18,000 lbs./ hr. of hydrogen in a treat gas stream as shown by line 108. Hydrogen purity is about 9,5%; the 18,000 lbs./hr. refers to the actual hydrogen content of the treat gas.

The hydrotreater contains a stationary bed of an alumina-supported cobalt molybdate catalyst, containing 2-5 weight percent cobalt oxide and 10-30 weight percent molybdenum oxide on an alumina support which is preferably presulded as well known in the art. The catalyst is in the form of I; inch diameter prills. The reaction conditions in the hydrotreater preferably include a temperature of about 730 F., a pressure of about 2000 p.s.i.g., a liquid hourly space velocity (LHSV) of about 0.3 volume of liquid 'per volume of catalyst per hour, and a hydrogen treat rate of about 10,000 s.c.f./ b. These conditions result in a hydrogen uptake of about 2000 s.c.f./b. From the hydrotreating zone 110, the products are removed by way of line 112 and passed into a liquid-gas separator 114. From the separator 114 are removed 30,000 lbs./l1r. of gas by Way of line 116. This gas contains ammonia, hydrogen sulfide, and C1-C4 hydrocarbon gases. The separator is operated at a' pressure of about 1800 p.s.i.g. A liquid stream containing 0.19 Weight percent nitrogen is removed by Way of line 118. This liquid stream is removed at the rate of 712,000 lbs/hr., and is introduced into the catalytic cracking unit 120, shown as a block in the diagram. The catalytic cracking unit will preferably be a uidized bed unit as commonly used in the art, but may be a transfer line type unit if desired. The catalytic cracking unit will comprise a burn-off regenerator and other associated equipment, all as is well known in the art. The coke yield, indicated as 30,000 lbs/hr. by way of line 122, is actually laid down on the catalyst particles and is removed by combustion in said regenerator.

From the catalytic cracking reactor, a product stream is removed by way of line 124 and is introduced into a fractionating system indicated as a single tower 126, although a plurality of towers can be used if desired. From the fractionator 126, 56,000 lbs./hr. of Cl-C., gas are moved overhead by way of line 128. A naphtha stream, having a clear Research Octane Number of 99.5 is removed'by way of line 130 at the rate of 265,000 lbs./hr. The naphtha stream boils within the range of C to 430 F. and contains 0.02 weight percent nitrogen and 10.5 weight percent hydrogen. A side stream heating oil product is removed at the rate of 245,000 lbs./hr. through line 132. This heating oil product contains 0.02 weight percent nitrogen and 8.6 weight percent hydrogen as compared to 0.35 weight percent nitrogen and 7.8 weight percent hydrogen in similar components of the fresh feed stream. The heating oil product is preferably completely recycled by way of line 104, although some or all could be withdrawn by way of line 134 if desired. The heavy unconverted feedstock is removed by way of line 136 as a bottoms stream at the rate of 116,000 lbs./hr. This Ibottoms stream contains 0.26 weight percent nitrogen and 6.4 weight percent hydrogen.

By operating the present invention as shown in the present embodiment, the production of naphtha is maximized and a high octane number naphtha is produced. The aromatics content in the naphtha product is about 75 volume percent, compared to 90 volume percent in the total fresh feedstock, thus showing that the aromaticity is substantially retained giving the high, clear Research Octane Number of this naphtha product.

The catalytic cracking unit reactor is operated under low severity conditions, and employs a zeolite type catalyst, preferably 5% synthetic faujasite encapsulated in a silica-alumina matrix. The catalyst is used in a fluidized bed under conditions comprising a temperature of about 950 to 1050 F., a pressure of about 20 to 40 p.s.i.g., a catalyst-to-oil ratio of about 8-10 pounds per pound and an oil residence time of about 30 minutes. The oncethrough 430 F.+ conversion is about 40%.

From the above description it can be seen that an efficient process scheme is provided whereby the liquid derived from coal liquefaction can yield a high octane Igasoline blend stock without the inclusion of lead-containing additives.

EXAMPLE were obtained.

TABLE V.CAT. CRACKING SHOWS BETTER REMOVAL OF NITROGEN FROM COAL LIQUIDS THAN FROM PETRO- LEUM STOCKS Feedstock:

Description.. Boiling range, F N2, wt. percent..

N2 removal from cat. cracking:

2) (2) 650/1, 000 40o/65o 0. 57 o. 11

Conversion (430 Fr), vol. percent. 38 40 N2 in 430/650 product, wt. percent- 0. 08 0. 22 0. 02

N2 in 650+ product. wt. percent.. 0. 28 0. 22 Ratio: N2 in unconverted feed cut/N2 in original feed.

l California H.G.O (H. G.O. is a heavy gas oil derived by fractionation oi a petroleum crude oil).

2 Coal liquids.

3 Typical range is Dir-1.4.

IReferring to the data summarized above, it is seen that the nitrogen content in the coal liquids is greatly reduced, as shown by the ratio of nitrogen in the unconverted feed divided by the nitrogen in the original feed. This reduction is not obtained in the case of petroleum liquids, such as California Heavy Gas Oil, as shown by the ratio 1.4 which indicates an increase, apparently due to selective cracking of nitrogen-free con-` stituents in the petroleum fractions. The heavy coal liquid boiling within the range of 650-l000 F. shows a ratio of 0.39, and the coal liquid boiling from 40G-650 F. shows a ratio of 0.18,-a great decrease in nitrogen content of unconverted material. It is this unexpected superiority in nitrogen removal which makes it feasible to recycle the heavy material from the catalytic cracking of coal liquids to obtain the desired dilution of the ammonia forming effect discussed above in the specification.

Having disclosed my invention, along with a preferred embodiment thereof, what is to be protected by Letters Patent is set forth in the following claims.

I claim:

1. A process for upgrading a coal-derived liquid oil stream boiling above about 400 F. and containing from about 50 to about 90 weight percent aromatic compounds which comprises:

(1) hydrotreating said liquid un'der conditions chosen lto obtain a nitrogen reduction of from about 30% to about 60%, and to obtain a hydrotreated product containing from about 9 to about 10 weight percent hydrogen, and

(2) catalytically cracking said liquid product under low severity reaction conditions to obtain a oncethrough conversion of about 25 to 50%, to products boiling below 430 F.

fractionating said catalytically cracked product to obtain at least a naphtha stream, a heating oil stream and a bottoms stream, said naphtha having an aromatic content of about 60 to 80 percent by w'eight,

and recycling to said hydrotreating zone at least a portion of said heating oil stream.

2. A process for upgrading a liquid oil stream obtained by the liquefaction of coal and boiling within the range from about 400 F. to about 1000" F., having a 50% point of at least 600 F. and containing from about 50 to about 90 weight percent aromatic compounds, which comprises:

contacting said liquid oil stream with a hydrotreating catalyst and hydrogen in a hydrotreating zone under hydrotreating conditions comprising a temperature from 675 to 775 F.,

a pressure from 1500 to 3500 p.s.i.g.,

a space velocity from 0.2 to 1.0 v./v./hr.,

a hydrogen treat rate from 5000 to 15,000 s.c.f./b.,

and

a hydrogen uptake from 1000 to 3000 s.c.f./b. to obtain a hydrotreated product of lower sulfur and nitrogen content than said liquid oil stream but containing at least 0.1 weight percent N2, contacting said hydrotreated product with a cracking catalyst in a catalytic cracking zone under cracking conditions comprising a temperature from 875 to 1050 F., a pressure from 5 to 60 p.s.i.g., a catalyst/oil ratio from 5 to 25 lbs/lb., and an average oil residence time from l5 to 60 minutes to obtain a catalytically cracked product at a once-through conversion of about 25 to 50% to products boiling below 430 F., fractionating said catalytically cracked product to obtain at least a naphtha stream, a heating oil stream and a bottoms stream, said naphtha having an aromatic content of about 60 to 80 percent by weight,

and recycling to said hydrotreating zone at least a portion of said heating oil stream.

3. A process for conversion of a coal-derived liquid oil stream, boiling above about 400 F., and containing from about 50 to about 90 weight percent aromatics, which comprises:

admixing said coal-derived liquid oil stream with a recycle heating oil stream, said recycle heating oil stream constituting from 25 to 45 volume percent of the total liquid admixture to a succeeding hydrotreating zone, passing said admixture through said hydrotreating zone in contact with molecular hydrogen and a hydrotreating catalyst,

at a temperature from about 675 to about 775 's a pressure from about 1500 to about 3500 p.s.i.g., a LHSV from about 0.2 to about 1.0 v./v./hr., a hydrogen treat rate from about 5000 to about 15,000 s.c.f./b., and a hydrogen uptake from about 1000 to about 3000 s.c.f./b., whereby a hydrotreated product is obtained having a hydrogen content from about 9 to about 10 weight percent,

passing said hydrotreated product through a catalytic cracking zone in contact with a cracking catalyst,

at a temperature from about 875 to about 1050 F., a pressure from about to about 60 p.s.i.g., a catalyst-to-oil ratio from about 5 to about 25 pounds per pound, an oil residence time from about to about 60 minutes, and a once-through 430 R+ conversion from about 25 to about 50%, whereby a cracked product is obtained, fractionating said cracked product to recover at least a naphtha stream, a heating oil stream, and a bottoms stream, said naphtha having an aromatic content of about 60 to 80 percent by weight, and recycling at least a portion of said heating oil stream for admixture with said coal-derived liquid oil stream.

4. A process in accordance with claim 3 wherein the hydrotreating catalyst is selected from the group consisting of the oxides and suldes of cobalt, molybdenum, nickel and tungsten, and mixtures thereof, and the cracking catalyst is selected from the group consisting of silicaalumina, silica-magnesia, cracking clay, crystalline aluminosilicate zeolites and mixtures thereof.

5. A process in accordance with claim 3 wherein the 10 hydrotrteating catalyst is a mixture of cobalt and molybdenum suldes supported on alumina and the cracking catalyst is a crystalline aluinosilicate zeolite encapsulated in a silica-alumina gel.

6. A process in accordance with claim 3 wherein said bottoms stream is at least in part recycled for admixture with said coal-derived liquid oil stream.

7. A process in accordance with claim 4 wherein substantially all of said heating oil stream is recycled.

8. A uprooess in accordance with claim 4 wherein substantially all of said heating oil stream and substantially all of said bottoms stream are recycled -for admixture with said coal-derived liquid oil stream.

9. A process in accordance with claim 8 wherein (a) the hydrotreating catalyst is a mixture of cobalt and molybdenum sulfide supported on alumina, hydrotreating conditions comprise:

a temperature of about 720 F.,

a pressure of about 2000 p.s.i.g.,

a LHSV of about 0.4 v./v./hr.,

a hydrogen treat rate of about 10,000 s.c.f./b., and

a hydrogen uptake of about 2000 s.c.f./b.; and

(b) the cracking catalyst is about 5% synthetic faujasite encapsulated in silica-alumina gel, cracking conditions comprise:

a temperature of about 950 F.,

a pressure of about 25 p.s.i.g.,

a catalyst-to-oil ratio of about 15 pounds per pound,

an oil residence time of about 30 minutes, and

a one-through 430 R+ conversion of about 40%.

I10. A process in accordance with claim 9 wherein said heating oil stream boils within the range from about 430 F. to about 650 F. and the bottoms stream boils within the range from about 650 F. to about 1000 F.

References Cited UNITED STATES PATENTS 3,071,536 l/1963 Stiles et al. 208-61 3,098,029 7/ 1963 Snyder, Jr. 208-58 3,506,568 4/1970 Annesser et al. 208-89 2,885,337 v5/1959 Keith et al. 208-61 DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner U.S. C1. X.R. 20S-57 

